Presently, research and development are advancing in organic EL display panel of the active matrix type, where each pixel is provided with an organic electroluminescence element (hereinafter, organic EL element) along with a drive circuit to drive the organic EL element. The organic EL element includes a bottom electrode, a top electrode, and an organic light-emitting layer disposed between the electrodes, as well as a functional layer that includes a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, and so on as needed. Typically, an organic EL display panel has a common electrode as the top electrode provided in common for all pixels, and a pixel electrode as the bottom electrode provided individually for each pixel. Also, top-emission configurations are often used to improve the pixel aperture ratio. In such cases, the common electrode acting as the top electrode is required to be optically transmissive. To ensure that the material is optically transmissive, using a transparent conductor such as indium tin oxide (hereinafter, ITO), indium zinc oxide (hereinafter, IZO), or zinc oxide. Alternatively, a 10 nm to 20 nm thin film of a metal such as silver, gold, or aluminium may be used. As it happens, transparent conductors such as ITO have high resistance relative to metal materials, which makes the common electrode prone to great drops in voltage toward the centre of the panel. Metal material such as silver has increased sheet resistance due to thinning, thus making the common electrode similarly prone to great drops in voltage toward the centre of the panel.
Conventionally, technology has been proposed for providing auxiliary wiring that reduces the voltage drop toward the centre of the panel (e.g., Patent Literature 1). FIG. 24 is a partial cross-sectional diagram showing the configuration of a organic EL display panel described in Patent Literature 1. Three pixels are shown.
The organic EL display panel includes a substrate 51, power supply wiring 52, a TFT layer 53, an inter-layer insulation film 54, a pixel electrode 55, auxiliary wiring 56, a partition layer 58, an organic light-emitting layer 60, and a common electrode 62. The pixel electrode 55 and the auxiliary wiring 56 are arranged at a distance from each other, on the inter-layer insulation film 54. The partition layer 58 is formed over the inter-layer insulation film 54, and has two types of openings, one type formed over the top of the pixel electrode 55 and the other type formed over the top of the auxiliary wiring 56. The organic light-emitting layer 60 is formed in each of the openings over the pixel electrode 55. Then, the common electrode 62 is formed so as to cover the partition layer 58, is electrically connected to the pixel electrode 55 via the organic light-emitting layer 60 through the openings over the pixel electrode 55, and electrically connected to the auxiliary wiring 56 through the openings over the auxiliary wiring 56. Although not illustrated, the auxiliary wiring 56 extends from a periphery of the panel to the centre of the panel. Providing the auxiliary wiring 56 in this way enables the combined resistance of the common electrode 62 and the auxiliary wiring 56 to be decreased in comparison to a configuration where the auxiliary wiring 56 is not provided, thereby diminishing the voltage drop toward the centre of the panel.